The objective of the proposed research is to examine the relationship between caffeine intake and human reproduction. Preliminary data indicate that caffeine may adversely affect female and male reproductive performance. The high prevalence of caffeine intake suggests that a large proportion of the population is potentially affected. This research is intended to estimate the effects of caffeine on risk of spontaneous abortion and on semen quality, and to examine the roles that caffeine metabolism and hormonal function might play in mediating any effects of caffeine on reproduction. There are four components: (1) The relationship of caffeine to spontaneous abortion will be examined by analyzing data collected from a prospective study of 5300 pregnant women. Subjects were members of an ethnically diverse health maintenance organization, recruited at first prenatal appointment and interviewed at 7-13 weeks gestation. Interview data will provide information on caffeine consumption and potential confounding variables. Caffeine intake and other risk factors will be compared in women with and without spontaneous abortion. Whether certain factors, such as the presence of nausea, changes in caffeine consumption or the type of caffeinated beverage consumed affect risk will also be examined. (2) The role of caffeine metabolism in determining the risk of spontaneous abortion will be examined by characterizing caffeine metabolism in a sample of approximately 140 cases and 140 controls from component 1. Each woman will submit a single first morning urine after ingestion of a test dose of caffeine. The major metabolites of caffeine will be determined, and the rate of caffeine metabolism and activities of three specific enzymes calculated from metabolite ratios. Whether a slower rate of metabolism or alteration in enzyme activity modify the risk for spontaneous abortion associated with caffeine ingestion will be determined. (3) The effect of caffeine on hormonal function and ovulation will be studied by analyzing data collected in a prospective study of approximately 400 women (from the same health plan) at risk of becoming pregnant. Daily first morning urine samples were collected for up to six months and will be analyzed for estrogen and progesterone metabolites, providing information on occurrence of ovulation and length of follicular and luteal phases. Interview data will provide information on caffeine consumption and potential confounding variables. Whether caffeine is associated with alteration in hormonal function, increases in anovulatory cycles, alterations in urinary steroid conjugate levels, or specific patterns of hormonal change will be examined. Saliva from these women will be assayed for caffeine to provide a biomarker of exposure. (4) The effect of caffeine on semen quality will be examined by analyzing data collected from a group of husbands of women from component 3. Semen samples have been collected from approximately 160 men, and will be analyzed for sperm count, motility, and morphometry, while semen and saliva will be analyzed for caffeine. Interview data will provide information on caffeine consumption and potential confounding variables. Data collection for components 1, 3, and 4 has been completed. Component 2 is a newly proposed study. The information gained from these studies could be used in the prevention of adverse reproductive effects of caffeine.